The objective of this proposal is to develop an intravascular imaging detector based on solid-state silicon sensor, to identify vulnerable coronary artery plaques. Currently, coronary angiography is unable to define the status of the atheroma and only measures the luminal dimensions of the blood vessel, without providing information about plaque content. The proposed new silicon detector will work by sensing beta particles from plaque-binding radiotracers. Thereby, a signature will be obtained for the 70% of heart attacks that are caused by minimally obstructive vulnerable plaques which are too small to be detected by angiography. This signature will enable targeted and cost effective therapies to prevent acute coronary artery diseases such as: unstable angina, acute myocardial infarction, and sudden cardiac death. In Phase I we will develop a prototype silicon sensor for detecting radiotracer emissions originating from vulnerable plaque, optimize the prototype sensor, prepare detector assemblies and characterize their performance using plaque labeling radiotracers in order to assess the feasibility of the approach for intravascular plaque detection. Preliminary studies show that for silicon the beta/gamma ratio is greatly improved over other technologies. In addition, the silicon offers other advantages such as reduced detector size for enhance clinical. In Phase II, a prototype catheter system will be fabricated and evaluated using animal models. PROPOSED COMMERCIAL APPLICATIONS: The commercial and medical value of a device that can enable preemptive treatment of coronary artery disease is self evident. Over 2 million catheterization diagnostic procedures are performed annually worldwide that would immediately quality for augmentation: with catheter based diagnosis of vulnerable plaque.